1. Field of the Invention
The present invention relates to a stripping composition for removing unnecessary substances in a semiconductor device, such as a resist left after etching and an etching residue.
2. Description of the Related Art
In a step for forming holes or wiring trenches or the like in the process for manufacturing a semiconductor device, a resist pattern is formed using lithography, dry etching is performed using the resist pattern as a mask, and the resist pattern as the mask is removed. In order to remove the resist pattern, a wet processing using a stripping solution after ashing with plasma or the like is generally performed. Heretofore, various stripping solutions have been developed and practically used, and for example, organic sulfonic acid-based stripping solutions containing an alkyl benzenesulfonic acid as the main component, organic amine-based stripping solution containing an amine such as monoethanol amine as the main component, or hydrofluoric acid-based stripping solutions containing hydrofluoric acid or a salt thereof as the main component have been known.
However, to meet recent demands for increasing the speed of semiconductor devices, as well as improving stripping properties from further integration and densification of semiconductor devices, low-resistance materials, such as copper, have been used more frequently as a wiring material. When via holes or the like are formed in interlayer insulating films on copper wiring, if etching residues, particularly of silicon and the oxides thereof, produced during the etching of the interlayer insulating films remain on the bottoms and sidewalls of the via holes, these etching residues interfere with the formation of films, such as barrier films formed in the following step; therefore, etching residues must be removed. However, if conventionally known stripping solutions are used for removing etching residues, a critical problem of the dissolution of copper wirings exposed on the bottoms of via holes arises. Therefore, from the viewpoint of preventing the corrosion of metal materials, such as copper wirings, by the stripping solution, compositions of stripping solutions containing anticorrosive substances have been proposed.
On the other hand, in order to utilize the feature of low resistance of copper wirings, it is required to lower the capacity between adjacent wirings, and materials having a low dielectric constant are generally used for interlayer insulating films formed around the wirings. These materials include, for example, inorganic materials, such as SiOC (carbon-containing SiO2); polyorganosiloxanes, such as MSQ (methyl silsesquioxane), HSQ (hydrogen silsesquioxane), and MHSQ (methylated hydrogen silsesquioxane); and aromatic organic materials, such a polyaryl ether (PAE) and divinyl siloxane-bis-benzocyclobutene (BCB). These low-dielectric materials have a problem of poor ashing resistance, and the dielectric constant increases when exposed to plasma. Therefore, it is desired to make ashing time as short as possible, and to make ashing conditions as moderate as possible; however, in this case, the treatment using a stripping solution having a strong strippability is essential.
As photoresist stripping solutions, and solutions for removing degenerated film after ashing, especially for removing residues of silicon and the oxides thereof, compositions containing fluorine compounds, such as hydrofluoric acid, are frequently used. The known examples include, for example, a semiconductor device cleaning agent containing a specific quaternary ammonium salt, a fluorine compound, and an organic solvent (Japanese Patent Application Laid-Open No. 7-201794); a resist stripping composition containing the salt of a base containing no metal ions and hydrofluoric acid, and a water-soluble organic solvent, of a pH of 5 to 8 (Japanese Patent Application Laid-Open No. 9-197681); a semiconductor device cleaning agent containing specific quantities of a fluorine compound, a water-soluble organic solvent, and water (Japanese Patent Application Laid-Open No. 11-67632); and a stripping solution containing a specific proportions of a specific quaternary ammonium hydroxide, a nucleophillic amine compound having an oxidation-reduction potential, sugars and/or sugar alcohols, and water (Japanese Patent Application Laid-Open No. 9-283507).
As stripping compositions imparted with an anticorrosive function of metal wirings, U.S. Pat. No. 5,417,877 discloses a stripping composition containing an amide and an amine as major components, whereto a component having a 5- or 6-member cyclic structure in the molecule thereof, and having a plurality of hetero atoms to coordinate to the wiring material metal and to form a 5- or 6-member cyclic coordinate complex; and Japanese Patent Application Laid-Open No. 10-171130 discloses a stripping composition containing an organic amine and a nitrogen-containing compound having a specific structure. However, no applications to fine and multi-layered wiring processes adopting copper wirings and low-dielectric films are considered in these patents, and even if the corrosion resistance of metal wirings is achieved, there are problems of incomplete removal of deposits on the surface of a substrate, and the occurrence of damage of the low-dielectric films.
Consequently, in conventional stripping solutions and cleaning solutions according to these patents, the low-dielectric films are not considered, and cannot prevent the corrosion of metal wirings formed on recent substrates of high integration and high densification.
Furthermore, stripping solutions and cleaning solutions containing fluorine compounds such as hydrofluoric acid have problems of easily corroding copper films and easily damaging the film quality of the materials of low-dielectric films.
The present inventors also found that even if the amine content was increased to improve the removal of unnecessary residues, such as deposits on the bottoms and sidewalls of via holes, there was a problem of increase in damage to the film quality of the materials of low-dielectric films.
As described above, if a method excels in removal of residues on the bottoms and sidewalls of via holes, there are problems of increase in corrosion of metal wirings and damage to the materials of low-dielectric films.
In order to solve these problems in prior art, the present inventors invented a stripping composition comprising a stripping agent, specifically an alkanolamine, a solvent, and an anticorrosive, wherein the anticorrosive was purine, a purine derivative, uric acid, or a uric acid derivative, and previously filed the application for patent (Japanese Patent Application No. 2001-196512). However, even if the stripping composition according to the prior invention was used, there was found the case where damage occurs or the removal of the deposits on the surface of the substrate was incomplete depending on the type of low-dielectric films.
Heretofore, although a resist stripping solution has been developed as a means for improving the corrosion resistance of wiring materials, in the situation where a low-dielectric film is used as an interlayer insulating film, the necessity to strip residues after ashing and resist residues in the state where the low-dielectric film is exposed during the stripping step has arisen. Therefore, the study of stripping solutions from a different point of view from the prior art is required.